In virtual concatenation of transport containers, a group of member containers is defined over which a data stream of higher bandwidth can be transported. This is done, for example, when transporting data over SONET/SDH networks. The virtual concatenation group member containers are transported as synchronous payload envelopes across the SONET/SDH network and recombined at the virtual concatenation group receiver. These virtual concatenation groups are further enriched by a link capacity adjustment scheme, which allows dynamic provisioning and reconfiguration of virtual concatenation groups, including dynamic changes in the bandwidth of virtual concatenation groups.
In order to keep track of the member container transmission order for a virtual concatenation group, each member container has associated with it a multi-frame identifier value. At the source side of a virtual concatenation link, all member containers are assigned the same multi-frame identifier value. Since each member container is routed over a network individually, each member container experiences its own specific amount of delay caused by differences in the physical transmission path length, intermediate equipment delay, and the like. These differences in transport delay must be compensated for in order to arrange the member containers of a virtual concatenation group in the correct order at the virtual concatenation group terminating equipment.
This differential delay compensation is typically done at the receiving side of the system by storing the member containers in a buffer memory as long as all of the members belonging to a specific virtual concatenation group have not yet been received. After the slowest member container is received, all members of that virtual concatenation group are then read from the buffer in the original order in which they were transmitted.
Using this process, the amount of differential delay that is compensated for at the virtual concatenation group receiving end, defined as the correction range of the receiving equipment, is limited by the size of the buffer in the virtual concatenation group receiving equipment. In practical networks, a situation may occur in which differential delay between some member containers of a virtual concatenation group is larger than the correction range of the receiving equipment to which the member containers are transmitted. This situation is exacerbated due to the dynamic nature of the differential delay of member containers as a result of changes in the path routing, changes to the bandwidth of the virtual concatenation group, and the like. When this condition exists, transmission using virtual concatenation fails since the virtual concatenation group member containers cannot be rearranged in the correct order at the receiving equipment.
In some cases, the source side and receive side of virtual concatenation groups are under the control of different network operators. This prevents the network operator with control of the source side from taking any measures (such as increasing the buffer size of the receiving equipment) to prevent the condition in which the differential delay of virtual concatenation group member containers is larger than the correction range of the receiving equipment. Furthermore, even for the case in which a network operator does have control over the receive side equipment of a virtual concatenation group, the receiving equipment may not be upgradeable.